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Sept. 1, 1959 F. J. FUCHS, JR.. ETAL' 2,902,077 MANDREL FOR MAKING SMALL RADIUS BENDS ,IN TUBES OF RECTANGULAR CONFIGURATION Filed May 25. 1954 if [j .Z' Z- d v 1 4 x f #z W Z# I 2 .55 1

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I NVENTOR5 FRANCIS J. FUCHS,JR. ROBERT HI.HALL,

BY I A OREY nited States Patent MANDREL FOR MAKING SMALL RADIUS BENDS IN TUBES OF RECTANGULAR CONFIGURATION Francis J. Fuchs, Jr., and Robert H. Hall, Winston-Salem,

N.C., assignors'to Western Electric Company, Incorporated, New York, N.Y., acorporation of New York Application May 25, 1954, Serial No. 432,272

'1 Claim. (Cl. 153-63) This invention relates to tube bending mandrels and more particularly to a mandrel for use in effecting small radius bends in thin-walled rectangular tubes such as wave guides. v

The exacting requirements of many applications of wave guide tubing necessitates the maintenance of the interior cross-sectional dimensions of such tubing within narrowly defined limits in order to prevent undesirable alterations in the electrical transmission characteristics of the tubing.

Thus wave guides may be used to transmit a number of different types of electromagnetic waves, each type of wave having a characteristic electric and magnetic field configuration. Two general types of electromagnetic waves are recognized, the so-called E waves and H waves. Electromagnetic waves are propagated along a rectangular wave guide, having a narrow side and a broad side, in such a manner that an electrical field component of the waves is parallel to the narrow side of the guide and a magnetic field component is parallel to the broad side of the guide. A wave guide bent in a plane parallel to the narrow, side thereof, that is, parallel to the plane of the electric field of the wave,'is termed an E bend, and a bend in a plane parallel to the broad side of the guide, that is, parallel to the plane of the magnetic field of the wave, is termed an H bend.

Advances in the electronics arts have resulted in the utilization of electromagnetic energy having relatively short wave lengths, for example on the order of one centimeter. Wave guides having proportionately small dimensions are necessary for the transmission of such energy.

Consequently, an'object of the present invention is to provide a mandrel for use in making small radius E bends in wave guide tubing.

In accordance with the above object, there is provided a rigid stem slidably insertable within a tube to be bent and having an arcuate tongue projecting from one extremity thereof, a first terminal link having arcuate bifurcated extremities and pivotally connected at one extremity thereof to the tongue of the stem, an intermediate or body link having arcuate lugs extending from opposite extremities thereof and pivotally connected by one of the lugs to the other extremity of the first terminal link, and a second terminal link having a bifurcated extremity pivotally connected to the other lug of the intermediate link.

Other objects and advantages of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawing, wherein:

Fig. 1 is a top plan View of a portion of the unactuated mandrel;

Fig. 2 is a front elevational View of a portion of the mandrel;

Fig. 3 is a cross-sectional view of the mandrel taken on line 3--3 of Fig. 1;

Fig. 4 is a cross-sectional view of a Wave guide bent upon a minimum radius and shows a plan view of the mandrel therein in an actuated position;

Fig. 5 is a perspective view of a portion of the stem of the mandrel;

Fig. 6 is a perspective view of the first terminal link;-

Fig. 7 is a perspective view of the intermediate link; and

Fig. 8 is a perspective View of the second terminal link.

Referring now to the drawing wherein like reference numerals refer to the same elements throughout the several views, the numeral 11 designates generally a rigid mandrel stern slidably insertable into a tube to be bent and having a first extremity thereof adapted for connection to a reciprocable mandrel (not shown). A second extremity of the stem is provided partially with a convex arcuate tongue 12 extending longitudinally of the stem. The tongue 12 has a circular aperture 13 extending transversely therethrough. The second extremity of the stem 11 is further provided with arcuate surfaces defining concavities 14 extending transversely thereof adjacent the tongue 12.

The numeral 16 designates generally a first terminal link having opposite extremities thereof provided with arcuate convex bifurcations 17 and 18 which are respectively provided with aligned apertures 19 and 21 extending transversely therethrough. The first terminal link 16 is provided with arcuate recesses 22 and 23 extending transversely thereof between the bifurcations 17 and 18, respectively. One side of the first terminal link 16 is provided with a curved surface 24 having a radius. of curvature equal to the minimum radius bend which the mandrel is intended to produce.

The numeral 26 designates generally an intermediate link having arcuate convex lugs 27 and 28 extending longitudinally from opposite extremities thereof, the lugs 27 and 28 being respectively provided with apertures 29 and 31 extending transversely therethrough. The intermediate link 26 is provided on opposite extremities thereof with concave surfaces 32 and 33 extending transversely thereof and adjacent the arcuate lugs 27 and 28, respectively. The lugs 27 and 28, together with the concave surfaces 32 and 33, define transversely extending concaveconvex projections 25 and 30. One side of the intermediate link 26 is provided with a curved surface 34 similar in configuration to the curved surface 24 of the first terminal link 16.

The numeral 36 designates generally a second terminal link having one extremity thereof provided with a convex surface 37 and having an opposite extremity thereof provided with arcuate convex bifurcations 38. The bifurcations 38 are provided with aligned circular apertures 39' extending transversely therethrough. The second terminal link 36 is further provided with an arcuate recess 41 extending transversely thereof between the bifurcations 38. One side of the second terminal link 36 is provided with a curved surface 42 similar in configuration to the curved surfaces 24 and 34 of the first terminal link 16 and the intermediate link 26, respectively.

The first terminal link 16 is pivotally connected to the rigid stem 11 by means of a first pivot pin 43 extending through the apertures 21 of the first terminal link 16 and through the aperture 13 of the stem 11 whereby the tongue 12 of the stem 11 is slidably positioned within the recess 23 formed between the bifurcations 18, which bifurcations are slidably positioned within the concavities 14 of the stem 11.

The intermediate link 26 is pivotally connected to the: first terminal link 16 by means of a second pivot pin 44 extending through the apertures 19 and the aperture 31 whereby the lug 28 of the intermediate link 26 is slidably positioned within the recess 22 of the first terminal link.

16 and the bifurcations 17 thereof are slidably engageable with the concave surfaces 33 of the intermediate link 26.

The second terminal link 36 is pivotally connected to intermediate link. 26 by means of a thirdpivot pin, 46 extending throughthe apertures 39 and the aperture.2 9,.

whereby the lug 2 7{ of the. intermediate. link 26 is slidably positioned within the r ecess 41 of the second terminal link 36 and the bifurcations 3,8. areslidably engageable with the concave surfaces 32;.

In OperationJtheassembled mandrel is connected, by. one extremity of the stem, 11, to a reciprocable mandrel shaft (not shown); A straightsect-ion of a wave guide tube to be bent is positioned in a. suitable bending apparatus such as that disclosed ina co-pending application of Francis J. Fuchs, IrL,Serial No. 262,247jfi1ed December 18, 1951, now EatentNo. 2,792,048. The mandrelis fed into the positioned' tube until the center line of the first pivot pin 43. is, oppositethe center of rotation about which. the tubeis tobeibent Fig. 4). The bendingappar atus is then actuated todraw the tubing over themandrel and, about a formingdiehaving, a predetermined radius. A section of tube as bent by the mandrel disclosed herein and in. the manner described above is shown in cross section in Fig. 4 and is designated by the numeral 47. The mandrel, disclosed in the present invention is suitable for making. bends of. various angles and of various radii above aminimum value, R minimum, for example inch, the minimum radius. being predetermined in accordance with the size of the particular forming die used and with the radius of curvature of the curved surfaces 24-, 34 and 42 of the first terminal link, the intermediate link or body link, and the end link, respectively.

Upon completion of the above described bending process, the mandrel is retracted from the bent tube 47.

and the tube is then removed from-the bending apparatus. It is to be understood that various additions and modifications may be made to the invention as describedherein without departing from the spirit and scope thereof.

What is claimed is:

A flexible mandrel for bending tubes of rectangular configuration comprising a rigid stem of rectangular configuration having one extremity thereof provided with a pair of concavities and a convex tongue extending between said concavities, a first terminal link of rectangular configuration having opposite extremities thereof provided with convex bifurcations defining arcuate recesses therebetween, said first terminal link having one side thereof provided with a: curved; surface havinga curvature corre sponding' to the minimum radius ofthe flexed mandrel; a; second terminal link of rectangular configuration having; one extremity thereof provided with convex bifurcations defining an arcuate recess therebetween, said second terminal link having one side thereof provided with a curved surface similar to the curved surface on said first terminal link, an intermediate, link of rectangular configuration having each of two opposite extremities thereof provided with a pair of concave surfaces and a convex lug extending therebetween; said intermediate link having one side thereof provided with a curved surface similar tothe curved-surfaces onsaid-firstand second terminal'links, and means to pivotally interconnect said stern and said.- first terminal link, said firstterminal link and said intermediate link, andsaidtintermediate link and said second terminal link ReferencestCited. in the. file offthis patent UNITED STATES PATENTS 173,916 Dollard Feb. 22'; 1876 292,418 Devine Jan. 22, 1884 522,247 Wilson July 3, 1894" 896,116 Jewitt Aug. 18, 1908' 1,021,450 Cox Mar. 26, 1912' 1,261,191 Vallone Apr. 2, 1918' 1,683,572 Mueller et al; Sept. 4; 1928f 2,444,907 Attridge July 13, 1948" FOREIGN PATENTS 5,019 Great Britain Apr..23, 1885. 365,395- France Sept. 7, 1906:. 

